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Long Island-New Jersey (LINJ) Coastal Drainages Study

Fact Sheet FS-012-94, by Paul Stackelberg and Mark Ayers

In 1991, the U.S. Geological Survey (USGS) began its
National Water-Quality Assessment (NAWQA ) program to (1) document the
quality of a large, representative part of the Nation's water resources;
(2) define water-quality trends; and (3) identify major factors that
affect water quality. In addressing these goals, the program will produce
information that will be useful to water policy makers and managers at
National, State, and local levels.

Studies of 60 hydrologic systems
that include parts of most major river and aquifer systems form the
building blocks of the NAWQA program. Study units range in size from about
1,000 mi ² (square miles) to more than 60,000 mi²
and represent 60 to 70 percent of the Nation's water use and population
served by public water supply. The first 20 studies were begun in 1991; 20
more were begun in 1994, and the remaining 20 are to begin in 1997.

DESCRIPTION OF THE STUDY UNIT

The Long
Island-New Jersey Coastal Drainages NAWQA study, one of 20 begun in 1994,
will be coordinated from the USGS office in West Trenton, N.J. The study
unit covers more than 6,000 mi² in New York and New Jersey
(fig. 1). It includes all of Long Island, Staten Island, and the coastal
drainages of New Jersey, excluding the Delaware River Basin. In 1990, the
population of study unit was more than 10 million, concentrated mostly on
Long Island and in northeastern New Jersey. In 1973, 28 percent of the
study unit was developed for residential and urban use, 7 percent was used
for industrial and commercial purposes, 14 percent was used for
agriculture, 34 percent was forested, 9 percent was wetland, and 8 percent
was classified as either surface-water bodies or miscellaneous land
use.

About 65 percent of the study unit lies within the Coastal Plain
Physiographic Province (fig. 1), 24 percent is within the Piedmont
Physiographic Province and 11 percent is within the New England
Physiographic Province. The northern half of the Piedmont and New England
Physiographic Provinces was ice-covered during the last glacial advance.
Surficial deposits on Long Island are glacial in origin with morainal
deposits to the north and outwash deposits to the south.

Average annual
precipitation ranges from 42 inches in the Coastal Plain to 52 inches in
north-central New Jersey, and annual snowfall ranges from 13 inches in
southeastern New Jersey to more than 50 inches in north-central New
Jersey. Generally, precipitation is evenly distributed throughout the
year. Annual average temperature ranges from 56 degrees Fahrenheit in
southern New Jersey to 50 degrees Fahrenheit in southern New York.

Hydrogeologic characteristics of provinces north of the Fall Line differ
greatly from those of the Coastal Plain (fig. 1). The New England
Physiographic Province is underlain by igneous and metamorphic rocks that
contain water-bearing weathered and fractured zones typically within 300
feet of the land surface. Aquifers in the Newark Group, which is present
in the Piedmont province, consist of shale and sandstone that contain
water in weathered joint and fracture systems within 200 to 300 feet of
the land surface. The valleys in the glaciated northern half of these two
provinces are underlain by stratified drift and glacial till. The
stratified drift, composed of poorly sorted sand and gravel with
interbedded silt, silty sand, and clay, forms valley-fill aquifers. These
aquifers are generally 30 to 40 feet thick, but as much as 300 feet thick
in some valleys.

The Coastal Plain (fig. 1) is underlain by a wedge of
unconsolidated sediments that form permeable units (aquifers) of sand and
gravel interbedded with poorly permeable (confining) units of silt and
clay. These interbedded, unconsolidated sediments differ
in thickness and areal extent, but generally dip and thicken
southeastward to a maximum thickness of about 6,500 feet at the coast. The
Coastal Plain aquifers in New Jersey are the Kirkwood-Cohansey aquifer
system, the Atlantic City 800-foot sand, the Wenonah-Mount Laurel
aquifer, the Englishtown aquifer system, and the Potomac-Raritan-Magothy
aquifer system. The Kirkwood-Cohansey aquifer system is largely
unconfined, but the other aquifers are confined except where they crop
out.

Glacial deposits overlie most of Long Island and form the unconfined
(water-table) aquifer and local water-bearing deposits of lesser extent,
including the Jameco aquifer. These systems are underlain by the Magothy
and Lloyd aquifers, which are generally confined.

The Coastal Plain
has relatively flat, thick, sandy soils that allow rapid infiltration of
rainfall, in fact, more than 90 percent of streamflow is derived from
groundwater discharge. The New England and Piedmont Physiographic
Provinces have relatively steep, thin, clayey soils, which produce runoff
more rapidly than Coastal Plain soils. Much of western Long Island and
northeastern New Jersey consists of urban areas in which psved
impesrmisble surfaces yield runoff rapidly.

The principal river systems
within the study unit are the Hackensack, Passaic, Raritan, Toms, Mullica,
and Great Egg Harbor Rivers in New Jersey. Many other smaller rivers and
streams drain the Coastal Plain, including the Peconic River on Long
Island.

The Hackensack River drains 202 mi², mostly within the
Piedmont Physiographic Province. The basin is heavily urbanized.
Downstream reaches of the river receive urban runoff and point-source
discharges. The basin contains three major water-supply reservoirs. The
Passaic River (950 mi²-drainage) starts in the mostly
forested New England Physiographic Province and flows through the Piedmont
Physiographic Province, which is densely populated and highly
industrialized. Many upstream reaches are relatively pristine, whereas
downstream reaches receive urban runoff and point-source discharges. The
Passaic basin contains seven major water-supply reservoirs. The Raritan
River drains 1,105 mi² across the New England, Piedmont, and
Coastal Plain Physiographic Provinces. Upstream reaches of the river
receive agricultural runoff, whereas downstream reaches receive urban
runoff and point-source discharges. The basin contains two major
water-supply reservoirs and receives a significant diversion, as much as
100 Mgal/d (million gallons per day), from the Delaware River for water
supply. Water-supply facilities in all three river systems are
inter-connected and transfer of water is common.

Rivers that drain the Coastal Plain of New Jersey include the Toms (192
mi²), Mullica (569 mi²), and Great Egg Harbor
(347 mi²) Rivers. Their combined drainage area includes most
of the Pinelands, an area of sandy lowlands covered with scrub pine and
oak. The drainage areas of Long Island rivers and streams are largely
residential with high population density and some commercial land use.
Water in much of the New Jersey Pinelands is of pristine quality, whereas
water
in other parts of the New Jersey Coastal Plain and in much of Long Island
have been affected by agricultural and lawn chemicals, septic-tank
effluent, and synthetic organic compounds from domestic and commercial
use.

Major water uses in the study unit include domestic, commercial,
industrial, mining, power production, and crop irrigation. In 1985, 73
percent of the 2,230 Mgal/d of freshwater used in all of New Jersey was
surface water and 27 percent was groundwater. Of the 961 Mgal/d used for
public supply in 1985, about 57 percent was surface water and 43 percent
was groundwater. However, about 77 percent of the public supply north of
the Fall Line was from surface-water sources, whereas, only 29 percent
south of the Fall Line was from surface-water sources. Total domestic and
commercial use in New Jersey, including deliveries from public supply, was
804 Mgal/d serving about 7.5 million people in the State. In 1985, 469
Mgal/d was withdrawn from Long Island's aquifers to serve nearly 3
million people living there.

Coordination among the USGS, water-management agencies, and other related
scientific organizations is essential to the NAWQA program. A study-unit
liaison committee consisting of representatives from Federal, State, and
local agencies, universities, and the private sector who have
water-resources responsibilities has been organized for this study.
Specific activities of the liaison committee include definition of major
water-quality issues, sharing of water-quality and other data, assisting
in the design of the study, and review of planning activities, findings,
and interpretations, including reports. The Long Island-New Jersey Coastal
Drainages study-unit liaison committee held its first meeting on May 13,
1994.

The
committee identified two broad water-quality issues that are priorities in
the study unit: (1) the effects of point discharges and nonpoint-source
runoff to streams and, ultimately, Barnegat Bay and the New York/New
Jersey Harbor Complex and; and (2) the vulnerability of public and
domestic water supplies to contamination from urban, industrial, and
agricultural land use. Nutrients and toxic substances are of great concern
as part of these issues, primarily because the current scientific
understanding
of processes governing the presence, distribution, fate, and biological
effects of these contaminants is limited.

The committee specifically
suggested that due to the wealth of available data the groundwater
component of the study should focus on analysis of existing data and on
collecting data on processes affecting the source, transport, and fate of
selected constituents within aquifer systems in the study unit. Major
groundwater needs identified include developing a better understanding of
(1) relations between shallow-groundwater quality and land-use patterns,
(2) spatial and temporal trends in groundwater quality, (3)
vulnerability of wells to contamination, (4) age-dating of groundwater,
and (5) groundwater/surface-water interactions. Major surface-water needs
identified include developing a better understanding of the effects of and
processes associated with (1) toxic materials (such as trace elements and
synthetic organic compounds), (2) nutrients, (3) sediments (particularly
those related to the transport and fate of toxic materials and nutrients),
(4) stormwater quality, and (5) interbasin transfers of water. A
suggested focus was to relate sources and loads of nutrients and toxic
materials to sediment quality, bioaccumulation in tissues, aquatic
community effects, land use, and other factors.

The large population,
extensive urban and industrial development, and, in some areas,
agricultural activities, are the main causes of water-quality problems in
the study unit. The NAWQA program can provide additional data and
understanding to facilitate solution of these problems. Initial efforts
will focus on identifying gaps in the data and developing a comprehensive
understanding of the issues from an already rich water-quality data
base.